If you are new to BMW or RWD take some time in an empty parking lot to practice skidding a bit. Or take a school, as the proper advice goes-- but at least practice in a safe environment so you know how it feels and don't panic when the back-end slides out a little on a left turn in traffic.

I don't mean to sound condescending and I think even the most seasoned BMW driver should be reminding themselves what oversteer feels like in the snow every winter in a safe environment... personally I look forward to it